Cloning of Gossypium hirsutum Sucrose Non-Fermenting 1-Related Protein Kinase 2 Gene (GhSnRK2) and Its Overexpression in Transgenic Arabidopsis Escalates Drought and Low Temperature Tolerance

Abstract

The molecular mechanisms of stress tolerance and the use of modern genetics approaches for the improvement of drought stress tolerance have been major focuses of plant molecular biologists. In the present study, we cloned the Gossypium hirsutum sucrose non-fermenting 1-related protein kinase 2 (GhSnRK2) gene and investigated its functions in transgenic Arabidopsis. We further elucidated the function of this gene in transgenic cotton using virus-induced gene silencing (VIGS) techniques. We hypothesized that GhSnRK2 participates in the stress signaling pathway and elucidated its role in enhancing stress tolerance in plants via various stress-related pathways and stress-responsive genes. We determined that the subcellular localization of the GhSnRK2-green fluorescent protein (GFP) was localized in the nuclei and cytoplasm. In contrast to wild-type plants, transgenic plants overexpressing GhSnRK2 exhibited increased tolerance to drought, cold, abscisic acid and salt stresses, suggesting that GhSnRK2 acts as a positive regulator in response to cold and drought stresses. Plants overexpressing GhSnRK2 displayed evidence of reduced water loss, turgor regulation, elevated relative water content, biomass, and proline accumulation. qRT-PCR analysis of GhSnRK2 expression suggested that this gene may function in diverse tissues. Under normal and stress conditions, the expression levels of stress-inducible genes, such as AtRD29A, AtRD29B, AtP5CS1, AtABI3, AtCBF1, and AtABI5, were increased in the GhSnRK2-overexpressing plants compared to the wild-type plants. GhSnRK2 gene silencing alleviated drought tolerance in cotton plants, indicating that VIGS technique can certainly be used as an effective means to examine gene function by knocking down the expression of distinctly expressed genes. The results of this study suggested that the GhSnRK2 gene, when incorporated into Arabidopsis, functions in positive responses to drought stress and in low temperature tolerance.

Overexpression of Tamarix hispida ThTrx5 Confers Salt Tolerance to Arabidopsis by Activating Stress Response Signals

“…Under salt stress, levels of SOD, CAT, POD, and GSSG contents in transgenic line plants were higher than levels in WT plants (Figure 2), indicating that ThTrx5 overexpression increased salt tolerance of A. thaliana. This result aligns with previously reported results demonstrating that transgenic Arabidopsis overexpressing GhSnRK2 showed obvious salt tolerance that was associated with stress response processes that reduced water loss, regulated cell turgor, maintained relative water content, and controlled proline accumulation [18]. In fact, the importance of glutathione to plant salt stress responses has also been demonstrated in tomato, as glutathione content increased significantly under high salt exposure [19].…”

Transcriptome analysis reveals that distinct metabolic pathways operate in salt-tolerant and salt-sensitive upland cotton varieties subjected to salinity stress

“…Some members in the hormone signaling pathway have been identified to participate in the response to salt stress. It has been reported that overexpressing of G. hirsutum sucrose non-fermenting 1-related protein kinase 2 (GhSnRK2), which acts as a positive regulator in ABA signaling pathway, exhibited increased tolerance to ABA and salt stresses [45]. However, the molecular basis of cotton tolerance to salt stress remains to be discovered.…”

Recent insights into cotton functional genomics: progress and future perspectives

“…Among different abiotic stresses, drought and salinity are the two main factors that affect the cotton production and it has become a challenging task to improve tolerance in cotton against these stresses. Previously, few stress-related genes such as GhCIPK6 (He et al, 2013), GbRLK (Zhao et al, 2013), GhMKK1 (Lu et al, 2013) and GhSnRK2 (Bello et al, 2014) have been reported in cotton (Table 3). A cotton Raf-like MAP3K (GhMAP3K40) gene positively regulates defence response but mediates reduced tolerance to biotic and abiotic stresses in transgenic Nicotiana benthamiana .…”

“…However, the overexpression of annexin-encoding (GhAnn1) gene showed higher chlorophyll content, increased peroxidase activities and lower lipid peroxidation levels, which ultimately increase the salt and drought stress tolerance in transgenic cotton . Previous studies have also reported that CBL-interacting protein kinase (GhCIPK6) and sucrose nonfermenting 1-related protein kinase 2 (SnRK2) genes are also involved in abiotic stress tolerance in cotton (Bello et al, 2014;He et al, 2013). Genes related to ethylene, abscisic acid and jasmonic acid signalling pathways have also played a significant role in drought tolerance .…”